There are three places to stay in this park, the Dakota Loops, the Elk Ridge Terraces, and Pa Co Chu Puk down the road.
The last of the three has zero climb, and likely most useful for very large RV’s.
I stayed at Dakota last year and like it so much I came back this year. The closer you get to the water (find a map online) the more leveling you will likely need to do if in an RV. There are level camp sites.
I drove up to Elk Ridge this trip. More trees up there. Pretty.
All three campgrounds have showers. Elk appears to have a play set.
Be aware if you reserve online, the camping fee does not include an entrance fee. If you’re staying a night or two, pay daily. After that, buy an annual pass.